Methods: We analyzed deliveries at Los Angeles County þ University of Southern California (LAC þ USC) Medical Center between January 1, 2001 and December 31, 2007. All liveborn singleton infants 34 0/7e37 6/7 weeks gestational age were included. We excluded multiple gestations, intrauterine fetal demise, and any infant with a known congenital anomaly. Data included maternal characteristics, such as age, gravidity, parity,